Optimized subset processing for de-duplication

ABSTRACT

Some embodiments of the present invention include a method for identifying duplicate records from a group of records in a database system. The method includes generating a cluster of records from a group of records based on one or more keys; splitting the cluster of records into multiple subsets of records with each subset of records having fewer number of records than the cluster of records, wherein the splitting the cluster of records into multiple subsets of records is based on a number of records in the cluster of records exceeding a threshold; causing duplicate sets of records in each of the subsets of records to be identified, wherein a duplicate set of records includes one or more records, and wherein when a duplicate set of records includes two or more records, the two or more records are duplicates of one another; merging all of the duplicate sets of records identified from the multiple subsets of records forming a first group of duplicate sets of records; and forming a representative set of records based on selecting a representative record from each of the duplicate sets in the first group of duplicate sets of records.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.

TECHNICAL FIELD

The present disclosure relates generally to data processing and more specifically relates to identifying duplicate information.

BACKGROUND

The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also be inventions.

Database systems may include databases that have millions of records. To maintain the efficiency and integrity of the databases, searches may be performed to identify and remove duplicate records. Comparison of records against all the other records one-by-one to determine duplication may be significantly time consuming and computing intensive. As such, database designers continuously try to develop techniques that can improve the performance of the database as related to identifying and removing duplicate records.

BRIEF SUMMARY

For some embodiments, methods and systems for identifying duplicate records in a database system may include generating a cluster of records from a group of records based on one or more keys; splitting the cluster of records into multiple subsets of records with each subset of records having fewer number of records than the cluster of records, wherein the splitting the cluster of records into multiple subsets of records is based on a number of records in the cluster of records exceeding a threshold; causing duplicate sets of records in each of the subsets of records to be identified, wherein a duplicate set of records includes one or more records, and wherein when a duplicate set of records includes two or more records, the two or more records are duplicates of one another; merging all of the duplicate sets of records identified from the multiple subsets of records forming a first group of duplicate sets of records; and forming a representative set of records based on selecting a representative record from each of the duplicate sets in the first group of duplicate sets of records. Other aspects and advantages of the present invention can be seen on review of the drawings, the detailed description and the claims, which follow.

BRIEF DESCRIPTION OF THE DRAWINGS

The included drawings are for illustrative purposes and serve only to provide examples of possible structures and process steps for the disclosed techniques. These drawings in no way limit any changes in form and detail that may be made to embodiments by one skilled in the art without departing from the spirit and scope of the disclosure.

FIG. 1 shows a diagram of an example computing system that may be used with some embodiments.

FIG. 2 shows a diagram of an example network environment that may be used with some embodiments.

FIG. 3A shows diagrams of an example of a de-duplication module, in accordance with some embodiments.

FIG. 3B shows another example of a de-duplication module that may be used to identify and remove duplicate records using a matching service, in accordance with some embodiments.

FIG. 3C shows another example of a de-duplication module that may be used to identify and remove duplicate records using subsets, in accordance with some embodiments.

FIG. 4 shows an example diagram of the clusters generated by the clustering module, in accordance with some embodiments.

FIG. 5A shows an example diagram of the duplicate sets generated by the duplicate matching module, in accordance with some embodiments.

FIG. 5B shows an example diagram of splitting a cluster into multiple subsets, in accordance with some embodiments.

FIG. 5C shows an example diagram of relationship among the cluster, subsets and related duplicate sets, in accordance with some embodiments.

FIG. 5D shows an example diagram of using a representative of a duplicate set to identify duplicate records, in accordance with some embodiments.

FIGS. 6A, 6B and 6C show an example diagram of a data structure that may be used to represent duplicate sets, in accordance with some embodiments.

FIG. 7 shows a flowchart of an example process for identifying duplicate records using clusters, subsets and representative set, in accordance with some embodiments.

FIG. 8A shows a system diagram illustrating architectural components of an applicable environment, in accordance with some embodiments.

FIG. 8B shows a system diagram further illustrating architectural components of an applicable environment, in accordance with some embodiments.

FIG. 9 shows a system diagram illustrating the architecture of a multi-tenant database environment, in accordance with some embodiments.

FIG. 10 shows a system diagram further illustrating the architecture of a multi-tenant database environment, in accordance with some embodiments.

DETAILED DESCRIPTION

Applications of systems and methods for identifying duplicate records in a group of records will be described with reference to example embodiments. These examples are being provided solely to add context and aid in the understanding of the present disclosure. It will thus be apparent to one skilled in the art that the techniques described herein may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the present disclosure. Other applications are possible, such that the following examples should not be taken as definitive or limiting either in scope or setting.

In the following detailed description, references are made to the accompanying drawings, which form a part of the description and in which are shown, by way of illustration, specific embodiments. Although these embodiments are described in sufficient detail to enable one skilled in the art to practice the disclosure, it is understood that these examples are not limiting, such that other embodiments may be used and changes may be made without departing from the spirit and scope of the disclosure.

As used herein, the term “multi-tenant database system” refers to those systems in which various elements of hardware and software of the database system may be shared by one or more customers. For example, a given application server may simultaneously process requests for a great number of customers, and a given database table may store rows for a potentially much greater number of customers.

The described subject matter may be implemented in the context of any computer-implemented system, such as a software-based system, a database system, a multi-tenant environment, or the like. Moreover, the described subject matter may be implemented in connection with two or more separate and distinct computer-implemented systems that cooperate and communicate with one another. One or more embodiments may be implemented in numerous ways, including as a process, an apparatus, a system, a device, a method, a computer readable medium such as a computer readable storage medium containing computer readable instructions or computer program code, or as a computer program product comprising a computer usable medium having a computer readable program code embodied therein.

In general, businesses use a CRM (Customer Relationship Management) system (also referred to as a database system or system) to manage business relationships and information associated with the business relationship. For example, this may include customer and prospect contact information, accounts, leads, and opportunities in one central location. The information may be stored in a database as objects. For example, the CRM system may include “account” object, “contact” object and “opportunities” object.

The “account” object may include information about an organization or person (such as customers, competitors, and partners) involved with a particular business. The “contact” object may include contact information, where each contact may be an individual associated with an “account”. The “opportunities” object includes information about a sale or a pending deal. Each object may be associated with fields. For example, the “accounts” object may include fields such as “company”, “zip”, “phone number”, “email address”, etc. The “contact” object may include fields such as “first name”, “last name”, “phone number”, “accountID”, etc. The “accountID” field of the “contact” object may be the ID of the account that is the parent of the contact. The “opportunity” object may include fields such as “amount”, “accountID”, etc. The “accountID” field of the “opportunity” object may be the ID of the account that is associated with the opportunity. Each field may be associated with a field value. For example, a field value for the “zip” field may be “94105”.

There may be millions of records (e.g., individual contacts) in an object (e.g., contact object). When a new contact is inserted into the contact object, a match rule (or matching rule) may be applied to identify duplicate contacts. A match rule may use criteria to determine how closely a field on a new or edited record matches the same field on an existing record, and, ultimately, whether the two records match. A match key may be used by a match rule to quickly return a list of possible duplicates. The match key may be based on one or more fields. For example, a match key that is based on a “company” field and a “zip” field in an “accounts” object may be “company (2,6) zip (1,3)” with the numbers inside the brackets referring to number of tokens and number of characters per token.

Before the match keys are applied to any objects, the field values of those objects may be normalized. For example, if the object includes the field “company”, then the normalization for the field “company” may include expanding the acronyms, having the first letter of each word be in lowercases, removing the suffices such as “Corporation”, “Incorporated”, “Inc”, “Limited”, “Ltd.”, etc., and removing the stop words such as “and”, “the”, “of”. Using this normalization example, the field value “Intel Corp.” is normalized to become “intel”, and the field value “IBM” is normalized to become “international business machine”.

After the field values are normalized, some standard or pre-defined match keys are automatically applied when the match rule is activated. An example of a pre-defined match key is “company (2, 6) zip (1, 3)” that is applied to the “account” object. For example, if the company name is “salesforce.com”, then applying the first portion “company (2, 6)” of the match key results in the string “salesf”, and if the company zip code is “94105-5188”, then applying the second portion “zip (1, 3)” of the match key results in the string “941”. The resulting key is therefore “salesf941”. The process of applying the standard match keys may be referred to as indexing.

When the match rule is activated, the match key is automatically applied to all existing records so that when the match rule runs, the database system can look for duplicate candidates among records with the same key. For example, when the above example match key is applied to the “company” and “zip” fields, the key “sales941” is generated to match duplicate records having the same value in the “company” and “zip” fields. Using the match key to identify duplicate candidates can prevent users from saving duplicate records based on the value of one or more fields.

Using match rules to identify duplicate candidates may be applicable when adding a new record or an edited record into an object to determine how closely a field on the new or edited record matches the same field on an existing record and whether the two records match. However, this approach may not be applicable when an organization has millions of records that need to be processed to remove duplicate records (also referred to as de-duplication or de-dupe). The identification of the duplicate records can be challenging and may significantly affect the performance of the CRM system. As will be described, the millions of records may need to be grouped into multiple clusters of fewer of records to enable faster and more efficient identification and removal of the duplicate records.

The disclosed embodiments may include systems and methods for identifying duplicate records in a group of records in a database system and may include generating a cluster of records from a group of records based on one or more keys; splitting the cluster of records into multiple subsets of records with each subset of records having fewer number of records than the cluster of records, wherein the splitting the cluster of records into multiple subsets of records is based on a number of records in the cluster of records exceeding a threshold; causing duplicate sets of records in each of the subsets of records to be identified, wherein a duplicate set of records includes one or more records, and wherein when a duplicate set of records includes two or more records, the two or more records are duplicates of one another; merging all of the duplicate sets of records identified from the multiple subsets of records forming a first group of duplicate sets of records; and forming a representative set of records based on selecting a representative record from each of the duplicate sets in the first group of duplicate sets of records.

The disclosed embodiments may include an apparatus for identifying duplicate records and include a processor, and one or more stored sequences of instructions which, when executed by the processor, cause the processor to generate a cluster of records from a group of records based on one or more keys; split the cluster of records into multiple subsets of records with each subset of records having fewer number of records than the cluster of records, wherein the splitting the cluster of records into multiple subsets of records is based on a number of records in the cluster of records exceeding a threshold; cause duplicate sets of records in each of the subsets of records to be identified, wherein a duplicate set of records includes one or more records, and wherein when a duplicate set of records includes two or more records, the two or more records are duplicates of one another; merge all of the duplicate sets of records identified from the multiple subsets of records forming a first group of duplicate sets of records; and form a representative set of records based on selecting a representative record from each of the duplicate sets in the first group of duplicate sets of records.

The disclosed embodiments may include a machine-readable medium carrying one or more sequences of instructions for identifying duplicate records in a group of records in a CRM system, which instructions, when executed by one or more processors, may cause the one or more processors to generate a cluster of records from a group of records based on one or more keys; split the cluster of records into multiple subsets of records with each subset of records having fewer number of records than the cluster of records, wherein the splitting the cluster of records into multiple subsets of records is based on a number of records in the cluster of records exceeding a threshold; cause duplicate sets of records in each of the subsets of records to be identified, wherein a duplicate set of records includes one or more records, and wherein when a duplicate set of records includes two or more records, the two or more records are duplicates of one another; merge all of the duplicate sets of records identified from the multiple subsets of records forming a first group of duplicate sets of records; and form a representative set of records based on selecting a representative record from each of the duplicate sets in the first group of duplicate sets of records.

While one or more implementations and techniques are described with reference to an embodiment in which identifying duplicate records using clustering, subsets, and duplicate sets is implemented in a system having an application server providing a front end for an on-demand database service capable of supporting multiple tenants, the one or more implementations and techniques are not limited to multi-tenant databases nor deployment on application servers. Embodiments may be practiced using other database architectures, i.e., ORACLE®, DB2® by IBM and the like without departing from the scope of the embodiments claimed.

Any of the above embodiments may be used alone or together with one another in any combination. The one or more implementations encompassed within this specification may also include embodiments that are only partially mentioned or alluded to or are not mentioned or alluded to at all in this brief summary or in the abstract. Although various embodiments may have been motivated by various deficiencies with the prior art, which may be discussed or alluded to in one or more places in the specification, the embodiments do not necessarily address any of these deficiencies. In other words, different embodiments may address different deficiencies that may be discussed in the specification. Some embodiments may only partially address some deficiencies or just one deficiency that may be discussed in the specification, and some embodiments may not address any of these deficiencies.

The described subject matter may be implemented in the context of any computer-implemented system, such as a software-based system, a database system, a multi-tenant environment, or the like. Moreover, the described subject matter may be implemented in connection with two or more separate and distinct computer-implemented systems that cooperate and communicate with one another. One or more implementations may be implemented in numerous ways, including as a process, an apparatus, a system, a device, a method, a computer readable medium such as a computer readable storage medium containing computer readable instructions or computer program code, or as a computer program product comprising a computer usable medium having a computer readable program code embodied therein.

FIG. 1 is a diagram of an example computing system that may be used with some embodiments of the present invention. The computing system 102 may be used by a user to initiate identifying and removing duplicate records associated with a multi-tenant database environment. For example, the multi-tenant database environment may be associated with the services provided by Salesforce.com®.

The computing system 102 is only one example of a suitable computing system, such as a mobile computing system, and is not intended to suggest any limitation as to the scope of use or functionality of the design. Neither should the computing system 102 be interpreted as having any dependency or requirement relating to any one or combination of components illustrated. The design is operational with numerous other general purpose or special purpose computing systems. Examples of well-known computing systems, environments, and/or configurations that may be suitable for use with the design include, but are not limited to, personal computers, server computers, hand-held or laptop devices, multiprocessor systems, microprocessor-based systems, set top boxes, programmable consumer electronics, mini-computers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like. For example, the computing system 102 may be implemented as a mobile computing system such as one that is configured to run with an operating system (e.g., iOS) developed by Apple Inc. of Cupertino, Calif. or an operating system (e.g., Android) that is developed by Google Inc. of Mountain View, Calif.

Some embodiments of the present invention may be described in the general context of computing system executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that performs particular tasks or implement particular abstract data types. Those skilled in the art can implement the description and/or figures herein as computer-executable instructions, which can be embodied on any form of computing machine readable media discussed below.

Some embodiments of the present invention may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices.

Referring to FIG. 1, the computing system 102 may include, but are not limited to, a processing unit 120 having one or more processing cores, a system memory 130, and a system bus 121 that couples various system components including the system memory 130 to the processing unit 120. The system bus 121 may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) locale bus, and Peripheral Component Interconnect (PCI) bus also known as Mezzanine bus.

The computing system 102 typically includes a variety of computer readable media. Computer readable media can be any available media that can be accessed by computing system 102 and includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer readable media may store information such as computer readable instructions, data structures, program modules or other data. Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by computing system 102. Communication media typically embodies computer readable instructions, data structures, or program modules.

The system memory 130 may include computer storage media in the form of volatile and/or nonvolatile memory such as read only memory (ROM) 131 and random access memory (RAM) 132. A basic input/output system (BIOS) 133, containing the basic routines that help to transfer information between elements within computing system 102, such as during start-up, is typically stored in ROM 131. RAM 132 typically contains data and/or program modules that are immediately accessible to and/or presently being operated on by processing unit 120. By way of example, and not limitation, FIG. 1 also illustrates operating system 134, application programs 135, other program modules 136, and program data 137.

The computing system 102 may also include other removable/non-removable volatile/nonvolatile computer storage media. By way of example only, FIG. 1 also illustrates a hard disk drive 141 that reads from or writes to non-removable, nonvolatile magnetic media, a magnetic disk drive 151 that reads from or writes to a removable, nonvolatile magnetic disk 152, and an optical disk drive 155 that reads from or writes to a removable, nonvolatile optical disk 156 such as, for example, a CD ROM or other optical media. Other removable/non-removable, volatile/nonvolatile computer storage media that can be used in the exemplary operating environment include, but are not limited to, USB drives and devices, magnetic tape cassettes, flash memory cards, digital versatile disks, digital video tape, solid state RAM, solid state ROM, and the like. The hard disk drive 141 is typically connected to the system bus 121 through a non-removable memory interface such as interface 140, and magnetic disk drive 151 and optical disk drive 155 are typically connected to the system bus 121 by a removable memory interface, such as interface 150.

The drives and their associated computer storage media discussed above and illustrated in FIG. 1, provide storage of computer readable instructions, data structures, program modules and other data for the computing system 102. In FIG. 1, for example, hard disk drive 141 is illustrated as storing operating system 144, application programs 145, other program modules 146, and program data 147. Note that these components can either be the same as or different from operating system 134, application programs 135, other program modules 136, and program data 137. The operating system 144, the application programs 145, the other program modules 146, and the program data 147 are given different numeric identification here to illustrate that, at a minimum, they are different copies.

A user may enter commands and information into the computing system 102 through input devices such as a keyboard 162, a microphone 163, and a pointing device 161, such as a mouse, trackball or touch pad or touch screen. Other input devices (not shown) may include a joystick, game pad, scanner, or the like. These and other input devices are often connected to the processing unit 120 through a user input interface 160 that is coupled with the system bus 121, but may be connected by other interface and bus structures, such as a parallel port, game port or a universal serial bus (USB). A monitor 191 or other type of display device is also connected to the system bus 121 via an interface, such as a video interface 190. In addition to the monitor, computers may also include other peripheral output devices such as speakers 197 and printer 196, which may be connected through an output peripheral interface 190.

The computing system 102 may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer 180. The remote computer 180 may be a personal computer, a hand-held device, a server, a router, a network PC, a peer device or other common network node, and typically includes many or all of the elements described above relative to the computing system 102. The logical connections depicted in

FIG. 1 includes a local area network (LAN) 171 and a wide area network (WAN) 173, but may also include other networks. Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets and the Internet.

When used in a LAN networking environment, the computing system 102 may be connected to the LAN 171 through a network interface or adapter 170. When used in a WAN networking environment, the computing system 102 typically includes a modem 172 or other means for establishing communications over the WAN 173, such as the Internet. The modem 172, which may be internal or external, may be connected to the system bus 121 via the user-input interface 160, or other appropriate mechanism. In a networked environment, program modules depicted relative to the computing system 102, or portions thereof, may be stored in a remote memory storage device. By way of example, and not limitation, FIG. 1 illustrates remote application programs 185 as residing on remote computer 180. It will be appreciated that the network connections shown are exemplary and other means of establishing a communications link between the computers may be used.

It should be noted that some embodiments of the present invention may be carried out on a computing system such as that described with respect to FIG. 1. However, some embodiments of the present invention may be carried out on a server, a computer devoted to message handling, handheld devices, or on a distributed system in which different portions of the present design may be carried out on different parts of the distributed computing system.

Another device that may be coupled with the system bus 121 is a power supply such as a battery or a Direct Current (DC) power supply) and Alternating Current (AC) adapter circuit. The DC power supply may be a battery, a fuel cell, or similar DC power source needs to be recharged on a periodic basis. The communication module (or modem) 172 may employ a Wireless Application Protocol (WAP) to establish a wireless communication channel. The communication module 172 may implement a wireless networking standard such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, IEEE std. 802.11-1999, published by IEEE in 1999.

Examples of mobile computing systems may be a laptop computer, a tablet computer, a Netbook, a smart phone, a personal digital assistant, or other similar device with on board processing power and wireless communications ability that is powered by a Direct Current (DC) power source that supplies DC voltage to the mobile computing system and that is solely within the mobile computing system and needs to be recharged on a periodic basis, such as a fuel cell or a battery.

FIG. 2 shows a diagram of an example network environment that may be used with some embodiments of the present invention. Network environment 400 includes computing systems 205 and 212. One or more of the computing systems 205 and 212 may be a mobile computing system. The computing systems 205 and 212 may be connected to the network 250 via a cellular connection or via a Wi-Fi router (not shown). The network 250 may be the Internet. The computing systems 205 and 212 may be coupled with server computing system 255 via the network 250.

The computing systems 205 may include application module 208. A user may use the computing system 205 and the application module 208 to connect to and communicate with the server computing system 255 and log into application 257 (e.g., a Salesforce.com® application). For example, the user may log into the application 257 to initiate the process of identifying and removing duplicate records in a group of records in a CRM system. The server computing system 255 may be coupled with database 270. The server computing system 255 may be associated with an entity (e.g., Salesforce.com®).

FIG. 3A shows an example of a de-duplication module that may be used to identify and remove duplicate records, in accordance with some embodiments. De-duplication module 300 may be associated with a computing system that is used by an administrator or a user who is responsible for removing duplicate records in a group of records 302. For some embodiments, the group of records 302 may be legacy records associated with a customer or an organization, and the de-duplication module 300 is configured to identify all of the duplicate records in the group and remove them. The group of records 302 may be stored in a database such as database 270 shown in FIG. 2. The group of records 302 may be associated with a web-based customer relationship management (CRM) database system 916 shown in FIG. 9.

The de-duplication module 300 may include clustering module 310 configured to generate multiple clusters from a group of records 302. For some embodiments, the records in the group of records 302 may be keyed into multiple keys. For example, when the records are employee records, the multiple keys may be associated with a last name, first name, account name, etc. The clustering module 310 may use match rules based on one or more keys to generate clusters of records. For example, when using a match rule that is keyed on the last name and based on a particular key value for last name (e.g., “Smith”), a first cluster of match candidates may be generated containing all records that have the same last name “Smith”. When using the same match rule that is keyed on the last name and based on a different key value (“Brown”), a second cluster of match candidates may be generated containing all records that have the same last name “Brown”. When using a match rule that is keyed on the account name and based on a particular key value for account name (e.g., “Salesforce.com®”), a third cluster of match candidates may be generated containing all records that have the same account name “Salesforce.com®”. It may be possible that the same record may be included in more than one cluster. That is, records in the different clusters may not be mutually exclusive. For example, a record having the last name value of “Smith” and the account name value of “Salesforce.com®” can be included in both the first cluster and the third cluster.

Using the clustering module 310 is advantageous because it filters the group of records 302 into clusters of duplicate candidates, each possibly having fewer (or a subset of) records comparing to the number of records in the group of records 302, making it easier to identify the actual duplicate records. For some embodiments, one or more keys may be used to generate the clusters. For example, there may be keys based on the last name and the account name.

A cluster generated by the clustering module 310 based on multiple keys may include fewer number of records than the clusters that are generated based on only one key. However, when the number of records is large and multiple keys are used, the process of generating a cluster of duplicate candidates may be time consuming and may not be as efficient generating clusters using fewer numbers of keys.

The de-duplication module 300 may include a duplicate matching module 315 configured to process the clusters generated by the clustering module 310. The duplicate matching module 315 may evaluate each record in a cluster and compare it with other records in the same cluster to identify duplicates. The matching operations performed by the duplicate matching module 315 may be referred to as deep matching because it filters the records included in the cluster to identify better duplicate candidates.

The duplicate matching module 315 may generate one or more duplicate sets for each cluster. Each duplicate set may include one or more records. A duplicate set with only one record may indicate that the record is unique within a given cluster. A duplicate set with multiple records may indicate that all those records are duplicates of one another within a given cluster. For example, assuming that there are two clusters, the duplicate matching module 315 may generate three duplicate sets after processing the first cluster and five duplicate sets after processing the second cluster, for a total of eight duplicate sets. Because the first and second clusters are generated based on different keys or key values, it is possible that the same record may be included in multiple duplicate sets.

The de-duplication module 300 may include a duplicate set merging module 320 configured to evaluate the duplicate sets generated by the duplicate matching module 315 and perform merging or consolidation of duplicate sets when necessary. The duplicate set merging module 320 may select a record in a duplicate set and determine of the same record exists in another duplicate set. If that situation exists, it may indicate that all of the records in the two duplicate sets are the same, and the two duplicate sets may be merged into a single duplicate set. It may be noted that once the duplicate set merging module 320 determines that the same record exists in two different duplicate sets, the merging operation may be performed without having to evaluate the other records in the two duplicate sets.

The de-duplication module 300 may include a duplicate removal module 325 configured to evaluate the duplicate sets after they are processed by the duplicate set merging module 320. It may be noted that each record in the group of records 302 including those included in the duplicate sets is associated with a unique address where it is stored in the database system. The address remains the same and does not change during the operation of the de-duplication module 300. For some embodiments, the duplicate removal module 325 may use the address information of the records in the duplicate sets to remove the duplicate records from the group of records 302.

FIG. 3B shows another example of a de-duplication module that may be used to identify and remove duplicate records using a matching service, in accordance with some embodiments. De-duplication module 301 is similar to the de-duplication module 300 of FIG. 3A except for the operation of the duplicate matching module 315 of FIG. 3A. Instead, the duplicate matching operations are performed by an external or third party matching service 316 which may be equipped to perform such matching operations more cost effectively. One example of such third party matching service is Pitney Bowes® with its Spectrum platform. It is possible that the external or third party matching service 316 may impose some requirements as to the number of records that it can receive and process. For example, the group of records 302 may include a million records, while the external or third party matching service 316 may only be able to perform matching operation for a group of 100,000 records at a time. Using this same example, it may be necessary for the clusters to be sufficiently filtered to have no more than 100,000 records per cluster. From the external or third party service 316, duplicate sets 319 may then be received and processed by the duplicate set merging module 320.

FIG. 3C shows another example of a de-duplication module that may be used to identify and remove duplicate records using subsets, in accordance with some embodiments. De-duplication module 303 is similar to the de-duplication module 300 of FIGS. 3A and 3B except for the additional subsetting module 311. Instead of transmitting the clusters from the clustering module 310 to the duplicate matching module 315 or the third party matching service 316, the clusters transmitted to the subsetting module 311 to split into multiple subsets. This may be necessary because the number of records in a cluster may vary and can be very large such that those records cannot be handled by the duplicate matching module 315 or the third party matching service 316. For some embodiments, a threshold may be used to determine whether the clusters need to be transmitted to the subsetting module 311. As shown in FIG. 3C, the subsets 313 from the subsetting module 311 may be transmitted to the duplicate matching module 315. Similarly, the subsets 312 from the subsetting module 311 may be transmitted to the duplicate matching service 316.

FIG. 4A shows an example diagram of the clusters generated by the clustering module, in accordance with some embodiments. The clustering module 310 may filter the group of records 302 to identify duplicate candidates. This may include identifying clusters of records based on keys and key values. All records that have a particular value (e.g., “Smith”) for the same key (e.g., last name) belong to the same cluster. For example, using a first key value, the clustering module 310 may generate a first cluster of records 405. Using a second key value, the clustering module 310 may generate a second cluster of records 410. Using a third key value, the clustering module 310 may generate a third cluster of records 415.

FIG. 5A shows an example diagram of the duplicate sets generated by the duplicate matching module, in accordance with some embodiments. In the example, the group of records 502 may include ten records as follows:

-   -   “A”, “B”, “C”, “D”, “E”, “F”, “G”, “H”, “I” and “J”.         The group of records 502 may be filtered for duplicate         candidates by the clustering module 310 (shown in FIG. 3) using         key and key values. This generates the clusters 503 and 504. The         cluster 503 may include the records “A”, “D”, “E”, “B”, “C” and         “F”. The cluster 503 may then be processed by the duplicate         matching module 315 (or third party matching service 316)         generating two duplicate sets 505 and 510.         The duplicate set 505 may include the records:     -   “A”, “D” and “E”.         The duplicate set 510 may include the records:     -   “B”, “C” and “F”.         The cluster 504 may include the records “G”, “H”, “E”, “I”, “J”         and “C”. The cluster 504 may then be processed by the duplicate         matching module 315 (or third party matching service 316)         generating two duplicate sets 515 and 520.         The duplicate set 515 may include the records:     -   “G”, “H” and “E”.         The duplicate set 520 may include the records:     -   “I”, “J” and “C”.         It may be noted that the record “E” is common in both the         duplicate set 505 and 515, and the record “C” is common in both         the duplicate set 510 and 520.

FIG. 5B shows an example diagram of splitting a cluster into multiple subsets, in accordance with some embodiments. It may be possible that the number of records in a cluster generated by the clustering module 310 may be too many that it may not be possible for these records to be efficiently processed by the duplicate matching module 315 (or the external or third party matching service 316). For example, a cluster may have 100,000 records while the matching module 315 may only be able to handle 10,000 records at a time. For some embodiments, it may be necessary for the records in a cluster to be split into multiple subsets, with each subset having fewer records. A threshold may be used to determine when splitting into smaller subsets may be necessary.

In general, the smaller the number of records in a subset, the less time it takes for the duplicate matching module 315 (or third party matching service 316) to identify and generate the duplicate sets. However, when the number of records in a subset is too small, the database system may require more time to merge the duplicate sets generated by the duplicate matching module 315 (or third party matching service 316). As shown in the example of FIG. 5B, the cluster 525 (generated by the clustering module 310) is shown to have ten records A, B, C, D, E, F G, J and I. The cluster 525 is split into “k choose 3” subsets or four (k=4) subsets, including subset 526 (with records A, B, C), subset 527 (with records D, E, F), subset 528 (with records G, H, K) and subset 529 (with record J). For some embodiments, there may be no overlapping of any record among the subsets, i.e., a record may not be included in two different subsets.

FIG. 5C shows an example diagram of relationship among the cluster, subsets and related duplicate sets, in accordance with some embodiments. For some embodiments, each of the subsets 526-529 may be processed by the duplicate matching module 315 (or third party matching service 316) to identify duplicate sets. For example, duplicate sets 530 may be generated from the subset 526. Similarly, duplicates sets 531 may be generated from the subset 527, duplicate sets 532 generated from the subset 528, and duplicate set 533 generated from the subset 529. For some embodiments, the duplicate sets generated from the subsets may be merged together into a merged duplicate set. For example, the duplicate sets 530-533 are merged into a merged duplicate sets 555 to include seven duplicate sets {{A, B}, C, D, E, F, {G, H, I}, J}.

FIG. 5D shows an example diagram of using a representative of a duplicate set to identify duplicate records, in accordance with some embodiments. As shown in FIG. 5D, the seven duplicate sets in the merged duplicate sets 555 (shown in FIG. 5C) are shown individually as duplicate sets 571-577. For some embodiments, any one record from a duplicate set is selected as a representative of the duplicate set. For example, the representative of the duplicate set 571 is the record “B” (shown in larger font size), and the representative of the duplicate set 576 is the record “H” (shown in larger font size). When a duplicate set has only one record, that record itself is the representative of the duplicate set. The representatives of all the duplicate sets are grouped together to form a representative set 580. In this example, the representative set 580 includes the records B, C, D, E, F, H and J.

For some embodiments, when the number of records in the representative set 580 is still too large for the duplicate matching module 315 (or third party matching service 316) to identify duplicate sets, the representative 580 may be split into smaller subsets. A threshold may be used to determine when splitting into smaller subsets may be necessary. It may be noted that the evaluation of the number of records in the representative set, the splitting of the representative set into smaller subsets, the processing of the subsets and the forming of another representative set shown in FIGS. 5C and 5D may be repeated until the number of records in the representative set is acceptable to be processed by the duplicate matching module 315 (or third party matching service 316).

When the representative set 580 is processed by the duplicate matching module 315 (or third party matching service 316), a duplicate set 585 may be generated. For example, the duplicate sets 585 may include the following duplicate sets {B,H}, {C}, {D,J}, and {E,F}. As may be noted in FIG. 5D, the duplicate sets 585 is derived from the representative set 580 which itself is derived from the merged duplicate set 555. For some embodiments, the duplicate sets 585 identified from the representative set 580 may be merged with the merged duplicate set 555 to form the duplicate set 595 as follows:

Duplicate sets 585: {B,H}, {C}, {D,J}, and {E,F} Duplicate sets 555: {{A, B}, C, D, E, F, {G, H, I}, J} Since the duplicate sets {B,H} and {A,B} share a common record B, they are merged to become {A,B,H}. Records that have been identified as duplicates remain in their duplicate sets. A record that is not a duplicate of any other records remains as a single record in its duplicate set. The merged or combined duplicate set 595 then includes the duplicate sets {A,B,H}, {C}, {D,J}, {E, F} and {G,H,I}. For some embodiments, the process of merging the duplicate sets 585 and the duplicate sets 555 may be repeated for each representative set 580 when a representative set 580 is split into multiple subsets.

FIG. 6A shows an example diagram of a data structure that may be used to represent duplicate sets, in accordance with some embodiments. As shown, there are four duplicate sets 645, 650, 655 and 660, each corresponding to the respective duplicate sets 505, 510, 515 and 520 shown in FIG. 5A. For some embodiments, each duplicate set may be implemented as a linked list with a head node followed by body nodes representing each record in the duplicate set. For example, the duplicate set 645 is implemented with a head node 601 followed by three body nodes 621, 622 and 623, with each corresponding to the respective records “A”, “D” and “E”.

A head node may include identification information for the associated duplicate set. For example, the head node 601 includes the value “0” as the identification information for the duplicate set 645. Similarly, the head node 602 includes the value “1” as the identification information for the duplicate set 650. Each head node may include information about the number of records included in (or the size of) the duplicate set. For example, the head node 601 includes the value “3” as the number of records in the duplicate set 645, and the head node 602 also includes the value “3” as the number of records in the duplicate set 650. Each head node may include a body pointer that links the head node to a first body node in the duplicate set. For example, the head node 601 includes a next node pointer 619 that links the head node 601 to the body node 621. The duplicate sets 645, 650, 655 and 660 are considered to be non-empty. When a duplicate set is empty, the body pointer may not be linked to any body node (e.g., its value may be set to null). For example, the body pointer of the head node 605 may be set to null.

A head node may also include a duplicate set pointer that links the head node to a head node of another duplicate set. For example, the head node 601 includes the duplicate set pointer 606 that links the head node 601 to the head node 602. The value of the duplicate set pointer 606 of the head node 605 may be set to null when there is no other head node to link to. Each head node many include information about a number of records included in (or the size of) the duplicate set. For example, the head node 601 includes the value “3” as the number of records for the records “A”, “D” and “E” in the duplicate set 645, and the head node 602 also includes the value “3” as the number of records for the records “B”, “C” and “F” in the duplicate set 650.

A body node may include information about a particular record in the duplicate set. For example, the body node 621 includes the value “A” as the information for the first record in the duplicate set 645. Similarly, the body node 622 includes the value “D” as the information for the second record in the duplicate set 645, and the body node 623 includes the value “E” as the information for the third record in the duplicate set 645. Each body node may include information about the duplicate set that it belongs to. This may include storing the identification information of the duplicate set. For example, each of the body nodes 621, 622 and 623 includes the value “0” as the identification information for the duplicate set 645. For some embodiments, this may include having a pointer that links to the corresponding head node. For example, instead of storing the value “0”, a head node pointer may be stored linking a body node such as the body node 622 to the head node 601. Each body node may include a next node pointer (e.g., next node pointer 620 of the body node 621) to point to the next body node in the duplicate set. The value of the next node pointer of the last body node in the duplicate set may be set to null. From the data structure shown in FIG. 6A, it may be noted that the record “E” is in both the duplicate sets 645 and 655, and the record “C” is in both the duplicate sets 650 and 660. It may be noted that even though the duplicate sets shown in FIG. 4 have the same size as “3”, it is possible for the duplicate sets to have difference sizes. For example, there may be a duplicate set with only one record. This may indicate that the record is unique within the cluster that was processed by the duplicate matching module 315 shown in FIG. 3A (or third party matching service 316 shown in FIG. 3B). For some embodiments, all the duplicate sets from all the clusters associated with the same group of records may be sorted based on the size of the duplicate sets. For example, the sorting may be based on an increasing size and may yield a duplicate set with the least number of records at the top of a sorted list. Merging may then be performed by starting with the duplicate sets positioned toward the top of the sorted list. For example, assuming there is a common duplicate set, a first duplicate set may be merged with a second duplicate set resulting in a combined duplicate set. The combined duplicate set may then be merged with a third duplicate set, and so on.

FIG. 6B shows an example diagram of a data structure reflecting the merging of two duplicate sets, in accordance with some embodiments. For some embodiments, the merging of duplicate sets may begin with selecting a record in a duplicate set and determine if that record also exists in another duplicate set. For example, when it is determined that the record “E” is common in both the duplicate sets 645 and 655, the duplicate sets 655 may be merged to the duplicate set 645, with the merged result shown as duplicate set 665 in FIG. 6B. It may be noted that the merged duplicate set 665 has five records “A”, “D”, “E”, “G” and “H”, and the size information is updated in the corresponding head node 601 as “5”. It may also be noted that the head node 603 is updated to reflect that it is associated with an empty duplicate set with size of “0” and with its next node pointer set to null.

For some embodiments, merging may occur by merging a duplicate set with few records to a duplicate set with more records. This approach is efficient as there are fewer nodes to merge, as compared to merging a duplicate set with more records to a duplicate set with few records. To determine the size of the two duplicate sets and which duplicate set has more records, the size information stored in the corresponding head nodes is evaluated. For some embodiments, merging may occur by setting the next node pointer of the last body node of one duplicate set to the first body node of the other duplicate set.

FIG. 6C shows an example diagram of a data structure reflecting the merging of two other duplicate sets, in accordance with some embodiments. For example, when it is determined that the record “C” is common in both the duplicate sets 650 and 660, the duplicate sets 660 may be merged to the duplicate set 650, the merged result shown as duplicate set 670 in FIG. 6C. It may be noted that the merged duplicate set 670 has five records “B”, “C”, “F”, “I” and “J”, and this size information is updated in the corresponding head node 602 as “5”. It may be noted that as soon as the record “C” in the duplicate set 660 is determined to also exist in the duplicate set 650, no further comparison is necessary with the other records in the duplicate set 650 because all records in both the duplicate sets 650 and 660 are transitively the same. It may also be noted that the head node 604 is updated to reflect that it is associated with an empty duplicate set with size of “0” and with its next node pointer set to null. When the merging operation is completed, each of the records in the group of records (e.g., group of records 502 shown in FIG. 5A) is accounted for in exactly one duplicate set.

FIG. 7 shows a flowchart of an example process for generating duplicate sets, in accordance with some embodiments. The example process 700 may be used to evaluate a group of records to determine whether the group of records includes duplicate records. The group of records may be associated with an organization and may need to be incorporated into a CRM database system. The records in the group of records may be indexed based on keys. The process may start at block 705 where the group of records may be evaluated based on a key (e.g., last name) and key value (e.g., Smith). All of the records matching the first value may then be grouped together to form a cluster. An example is shown as the clusters 503, 504 in FIG. 5A.

At block 710, it is determined that the number of records in the cluster is more than can be efficiently processed by the duplicate matching module 315 (or third party matching service 316). As a result, the cluster is split into multiple subsets, with each subset having fewer records than the number of records in the cluster. An example is shown as the multiple subsets 526-529 in FIG. 5B.

At block 715, each of the subsets is transmitted to the duplicate matching module 315 (or third party matching service 316) to generate duplicate sets. Each duplicate set may include one or more records. Records in the same duplicate set are considered to be the same. An example is shown as the duplicate sets 530-533 in FIG. 5C.

At block 720, the duplicate sets generated from the subsets are merged together to form merged duplicate sets. Duplicate sets that share a common record may be merged to one another. Duplicate sets that have a single record may remain the same. An example is shown as the merged duplicate sets 555 in FIG. 5C. The merged duplicate sets may be referred to as a first duplicate set. An example is shown as the duplicate set 555 in FIG. 5D.

At block 725, a representative from each of the duplicate sets in the merged duplicate sets is selected to form a representative set. An example is shown as the representative set 580 in FIG. 5D. At block 730, the representative set may be processed by the duplicate matching module 315 (or third party matching service 316) to form a group of duplicate sets. This may be referred to as a second group of duplicate sets. An example is shown as the duplicate sets 585 in FIG. 5D. At block 735, the first group of duplicate sets and the second group of duplicate sets may be merged to one another to generate a combined duplicate set. An example is shown as the combined duplicate sets 595 in FIG. 5D. One or more records in a merged duplicate list may be removed to prevent redundancy. Removing a record from a merged duplicate list may include removing that record from the group of records (e.g., group of records 502 shown in FIG. 5A). As described with FIG. 5D, it may be possible that the number of records in the representative set may need to be split into subsets. When that occurs, the process may flow from block 725 to block 710 (shown as the dotted line 740).

FIG. 8A shows a system diagram 800 illustrating architectural components of an on-demand service environment, in accordance with some embodiments. A client machine located in the cloud 804 (or Internet) may communicate with the on-demand service environment via one or more edge routers 808 and 812. The edge routers may communicate with one or more core switches 820 and 824 via firewall 816. The core switches may communicate with a load balancer 828, which may distribute server load over different pods, such as the pods 840 and 844. The pods 840 and 844, which may each include one or more servers and/or other computing resources, may perform data processing and other operations used to provide on-demand services. Communication with the pods may be conducted via pod switches 832 and 836. Components of the on-demand service environment may communicate with a database storage system 856 via a database firewall 848 and a database switch 852.

As shown in FIGS. 8A and 8B, accessing an on-demand service environment may involve communications transmitted among a variety of different hardware and/or software components. Further, the on-demand service environment 800 is a simplified representation of an actual on-demand service environment. For example, while only one or two devices of each type are shown in FIGS. 8A and 8B, some embodiments of an on-demand service environment may include anywhere from one to many devices of each type. Also, the on-demand service environment need not include each device shown in FIGS. 8A and 8B, or may include additional devices not shown in FIGS. 8A and 8B.

Moreover, one or more of the devices in the on-demand service environment 800 may be implemented on the same physical device or on different hardware. Some devices may be implemented using hardware or a combination of hardware and software. Thus, terms such as “data processing apparatus,” “machine,” “server” and “device” as used herein are not limited to a single hardware device, but rather include any hardware and software configured to provide the described functionality.

The cloud 804 is intended to refer to a data network or plurality of data networks, often including the Internet. Client machines located in the cloud 804 may communicate with the on-demand service environment to access services provided by the on-demand service environment. For example, client machines may access the on-demand service environment to retrieve, store, edit, and/or process information.

In some embodiments, the edge routers 808 and 812 route packets between the cloud 804 and other components of the on-demand service environment 800. The edge routers 808 and 812 may employ the Border Gateway Protocol (BGP). The BGP is the core routing protocol of the Internet. The edge routers 808 and 812 may maintain a table of IP networks or ‘prefixes’ which designate network reachability among autonomous systems on the Internet.

In one or more embodiments, the firewall 816 may protect the inner components of the on-demand service environment 800 from Internet traffic. The firewall 816 may block, permit, or deny access to the inner components of the on-demand service environment 800 based upon a set of rules and other criteria. The firewall 816 may act as one or more of a packet filter, an application gateway, a stateful filter, a proxy server, or any other type of firewall.

In some embodiments, the core switches 820 and 824 are high-capacity switches that transfer packets within the on-demand service environment 800. The core switches 820 and 824 may be configured as network bridges that quickly route data between different components within the on-demand service environment. In some embodiments, the use of two or more core switches 820 and 824 may provide redundancy and/or reduced latency.

In some embodiments, the pods 840 and 844 may perform the core data processing and service functions provided by the on-demand service environment. Each pod may include various types of hardware and/or software computing resources. An example of the pod architecture is discussed in greater detail with reference to FIG. 8B.

In some embodiments, communication between the pods 840 and 844 may be conducted via the pod switches 832 and 836. The pod switches 832 and 836 may facilitate communication between the pods 840 and 844 and client machines located in the cloud 804, for example via core switches 820 and 824. Also, the pod switches 832 and 836 may facilitate communication between the pods 840 and 844 and the database storage 856.

In some embodiments, the load balancer 828 may distribute workload between the pods 840 and 844. Balancing the on-demand service requests between the pods may assist in improving the use of resources, increasing throughput, reducing response times, and/or reducing overhead. The load balancer 828 may include multilayer switches to analyze and forward traffic.

In some embodiments, access to the database storage 856 may be guarded by a database firewall 848. The database firewall 848 may act as a computer application firewall operating at the database application layer of a protocol stack. The database firewall 848 may protect the database storage 856 from application attacks such as structure query language (SQL) injection, database rootkits, and unauthorized information disclosure.

In some embodiments, the database firewall 848 may include a host using one or more forms of reverse proxy services to proxy traffic before passing it to a gateway router. The database firewall 848 may inspect the contents of database traffic and block certain content or database requests. The database firewall 848 may work on the SQL application level atop the TCP/IP stack, managing applications' connection to the database or SQL management interfaces as well as intercepting and enforcing packets traveling to or from a database network or application interface.

In some embodiments, communication with the database storage system 856 may be conducted via the database switch 852. The multi-tenant database system 856 may include more than one hardware and/or software components for handling database queries. Accordingly, the database switch 852 may direct database queries transmitted by other components of the on-demand service environment (e.g., the pods 840 and 844) to the correct components within the database storage system 856. In some embodiments, the database storage system 856 is an on-demand database system shared by many different organizations. The on-demand database system may employ a multi-tenant approach, a virtualized approach, or any other type of database approach. An on-demand database system is discussed in greater detail with reference to FIGS. 9 and 10.

FIG. 8B shows a system diagram illustrating the architecture of the pod 844, in accordance with one embodiment. The pod 844 may be used to render services to a user of the on-demand service environment 800. In some embodiments, each pod may include a variety of servers and/or other systems. The pod 844 includes one or more content batch servers 864, content search servers 868, query servers 872, file force servers 876, access control system (ACS) servers 880, batch servers 884, and app servers 888. Also, the pod 844 includes database instances 890, quick file systems (QFS) 892, and indexers 894. In one or more embodiments, some or all communication between the servers in the pod 844 may be transmitted via the switch 836.

In some embodiments, the application servers 888 may include a hardware and/or software framework dedicated to the execution of procedures (e.g., programs, routines, scripts) for supporting the construction of applications provided by the on-demand service environment 800 via the pod 844. Some such procedures may include operations for providing the services described herein. The content batch servers 864 may requests internal to the pod. These requests may be long-running and/or not tied to a particular customer. For example, the content batch servers 864 may handle requests related to log mining, cleanup work, and maintenance tasks.

The content search servers 868 may provide query and indexer functions. For example, the functions provided by the content search servers 868 may allow users to search through content stored in the on-demand service environment. The Fileforce servers 876 may manage requests information stored in the Fileforce storage 878. The Fileforce storage 878 may store information such as documents, images, and basic large objects (BLOBs). By managing requests for information using the Fileforce servers 876, the image footprint on the database may be reduced.

The query servers 872 may be used to retrieve information from one or more file systems. For example, the query system 872 may receive requests for information from the app servers 888 and then transmit information queries to the NFS 896 located outside the pod. The pod 844 may share a database instance 890 configured as a multi-tenant environment in which different organizations share access to the same database. Additionally, services rendered by the pod 844 may require various hardware and/or software resources. In some embodiments, the ACS servers 880 may control access to data, hardware resources, or software resources.

In some embodiments, the batch servers 884 may process batch jobs, which are used to run tasks at specified times. Thus, the batch servers 884 may transmit instructions to other servers, such as the app servers 888, to trigger the batch jobs. In some embodiments, the QFS 892 may be an open source file system available from Sun Microsystems® of Santa Clara, Calif. The QFS may serve as a rapid-access file system for storing and accessing information available within the pod 844. The QFS 892 may support some volume management capabilities, allowing many disks to be grouped together into a file system. File system metadata can be kept on a separate set of disks, which may be useful for streaming applications where long disk seeks cannot be tolerated. Thus, the QFS system may communicate with one or more content search servers 868 and/or indexers 894 to identify, retrieve, move, and/or update data stored in the network file systems 896 and/or other storage systems.

In some embodiments, one or more query servers 872 may communicate with the NFS 896 to retrieve and/or update information stored outside of the pod 844. The NFS 896 may allow servers located in the pod 844 to access information to access files over a network in a manner similar to how local storage is accessed. In some embodiments, queries from the query servers 822 may be transmitted to the NFS 896 via the load balancer 820, which may distribute resource requests over various resources available in the on-demand service environment. The NFS 896 may also communicate with the QFS 892 to update the information stored on the NFS 896 and/or to provide information to the QFS 892 for use by servers located within the pod 844.

In some embodiments, the pod may include one or more database instances 890. The database instance 890 may transmit information to the QFS 892. When information is transmitted to the QFS, it may be available for use by servers within the pod 844 without requiring an additional database call. In some embodiments, database information may be transmitted to the indexer 894. Indexer 894 may provide an index of information available in the database 890 and/or QFS 892. The index information may be provided to file force servers 876 and/or the QFS 892.

FIG. 9 shows a block diagram of an environment 910 wherein an on-demand database service might be used, in accordance with some embodiments. Environment 910 includes an on-demand database service 916. User system 912 may be any machine or system that is used by a user to access a database user system. For example, any of user systems 912 can be a handheld computing system, a mobile phone, a laptop computer, a work station, and/or a network of computing systems. As illustrated in FIGS. 9 and 10, user systems 912 might interact via a network 914 with the on-demand database service 916.

An on-demand database service, such as system 916, is a database system that is made available to outside users that do not need to necessarily be concerned with building and/or maintaining the database system, but instead may be available for their use when the users need the database system (e.g., on the demand of the users). Some on-demand database services may store information from one or more tenants stored into tables of a common database image to form a multi-tenant database system (MTS). Accordingly, “on-demand database service 916” and “system 916” will be used interchangeably herein. A database image may include one or more database objects. A relational database management system (RDBMS) or the equivalent may execute storage and retrieval of information against the database object(s). Application platform 918 may be a framework that allows the applications of system 916 to run, such as the hardware and/or software, e.g., the operating system. In an implementation, on-demand database service 916 may include an application platform 918 that enables creation, managing and executing one or more applications developed by the provider of the on-demand database service, users accessing the on-demand database service via user systems 912, or third party application developers accessing the on-demand database service via user systems 912.

One arrangement for elements of system 916 is shown in FIG. 9, including a network interface 920, application platform 918, tenant data storage 922 for tenant data 923, system data storage 924 for system data 925 accessible to system 916 and possibly multiple tenants, program code 926 for implementing various functions of system 916, and a process space 928 for executing MTS system processes and tenant-specific processes, such as running applications as part of an application hosting service. Additional processes that may execute on system 916 include database indexing processes.

The users of user systems 912 may differ in their respective capacities, and the capacity of a particular user system 912 might be entirely determined by permissions (permission levels) for the current user. For example, where a call center agent is using a particular user system 912 to interact with system 916, the user system 912 has the capacities allotted to that call center agent. However, while an administrator is using that user system to interact with system 916, that user system has the capacities allotted to that administrator. In systems with a hierarchical role model, users at one permission level may have access to applications, data, and database information accessible by a lower permission level user, but may not have access to certain applications, database information, and data accessible by a user at a higher permission level. Thus, different users may have different capabilities with regard to accessing and modifying application and database information, depending on a user's security or permission level.

Network 914 is any network or combination of networks of devices that communicate with one another. For example, network 914 can be any one or any combination of a LAN (local area network), WAN (wide area network), telephone network, wireless network, point-to-point network, star network, token ring network, hub network, or other appropriate configuration. As the most common type of computer network in current use is a TCP/IP (Transfer Control Protocol and Internet Protocol) network (e.g., the Internet), that network will be used in many of the examples herein. However, it should be understood that the networks used in some embodiments are not so limited, although TCP/IP is a frequently implemented protocol.

User systems 912 might communicate with system 916 using TCP/IP and, at a higher network level, use other common Internet protocols to communicate, such as HTTP, FTP, AFS, WAP, etc. In an example where HTTP is used, user system 912 might include an HTTP client commonly referred to as a “browser” for sending and receiving HTTP messages to and from an HTTP server at system 916. Such an HTTP server might be implemented as the sole network interface between system 916 and network 914, but other techniques might be used as well or instead. In some embodiments, the interface between system 916 and network 914 includes load sharing functionality, such as round-robin HTTP request distributors to balance loads and distribute incoming HTTP requests evenly over a plurality of servers. At least as for the users that are accessing that server, each of the plurality of servers has access to the MTS' data; however, other alternative configurations may be used instead.

In some embodiments, system 916, shown in FIG. 9, implements a web-based customer relationship management (CRM) system. For example, in some embodiments, system 916 includes application servers configured to implement and execute CRM software applications as well as provide related data, code, forms, web pages and other information to and from user systems 912 and to store to, and retrieve from, a database system related data, objects, and Webpage content. With a multi-tenant system, data for multiple tenants may be stored in the same physical database object, however, tenant data typically is arranged so that data of one tenant is kept logically separate from that of other tenants so that one tenant does not have access to another tenant's data, unless such data is expressly shared. In certain embodiments, system 916 implements applications other than, or in addition to, a CRM application. For example, system 916 may provide tenant access to multiple hosted (standard and custom) applications. User (or third party developer) applications, which may or may not include CRM, may be supported by the application platform 918, which manages creation, storage of the applications into one or more database objects and executing of the applications in a virtual machine in the process space of the system 916.

Each user system 912 could include a desktop personal computer, workstation, laptop, PDA, cell phone, or any wireless access protocol (WAP) enabled device or any other computing system capable of interfacing directly or indirectly to the Internet or other network connection. User system 912 typically runs an HTTP client, e.g., a browsing program, such as Microsoft's Internet Explorer® browser, Mozilla's Firefox® browser, Opera's browser, or a WAP-enabled browser in the case of a cell phone, PDA or other wireless device, or the like, allowing a user (e.g., subscriber of the multi-tenant database system) of user system 912 to access, process and view information, pages and applications available to it from system 916 over network 914.

Each user system 912 also typically includes one or more user interface devices, such as a keyboard, a mouse, trackball, touch pad, touch screen, pen or the like, for interacting with a graphical user interface (GUI) provided by the browser on a display (e.g., a monitor screen, LCD display, etc.) in conjunction with pages, forms, applications and other information provided by system 916 or other systems or servers. For example, the user interface device can be used to access data and applications hosted by system 916, and to perform searches on stored data, and otherwise allow a user to interact with various GUI pages that may be presented to a user. As discussed above, embodiments are suitable for use with the Internet, which refers to a specific global internetwork of networks. However, it should be understood that other networks can be used instead of the Internet, such as an intranet, an extranet, a virtual private network (VPN), a non-TCP/IP based network, any LAN or WAN or the like.

According to some embodiments, each user system 912 and all of its components are operator configurable using applications, such as a browser, including computer code run using a central processing unit such as an Intel Pentium® processor or the like. Similarly, system 916 (and additional instances of an MTS, where more than one is present) and all of their components might be operator configurable using application(s) including computer code to run using a central processing unit such as processor system 917, which may include an Intel Pentium® processor or the like, and/or multiple processor units.

A computer program product implementation includes a machine-readable storage medium (media) having instructions stored thereon/in which can be used to program a computer to perform any of the processes of the embodiments described herein. Computer code for operating and configuring system 916 to intercommunicate and to process web pages, applications and other data and media content as described herein are preferably downloaded and stored on a hard disk, but the entire program code, or portions thereof, may also be stored in any other volatile or non-volatile memory medium or device, such as a ROM or RAM, or provided on any media capable of storing program code, such as any type of rotating media including floppy disks, optical discs, digital versatile disk (DVD), compact disk (CD), microdrive, and magneto-optical disks, and magnetic or optical cards, nanosystems (including molecular memory ICs), or any type of media or device suitable for storing instructions and/or data. Additionally, the entire program code, or portions thereof, may be transmitted and downloaded from a software source over a transmission medium, e.g., over the Internet, or from another server, or transmitted over any other conventional network connection (e.g., extranet, VPN, LAN, etc.) using any communication medium and protocols (e.g., TCP/IP, HTTP, HTTPS, Ethernet, etc.). It will also be appreciated that computer code for implementing embodiments can be implemented in any programming language that can be executed on a client system and/or server or server system such as, for example, C, C++, HTML, any other markup language, Java™, JavaScript®, ActiveX®, any other scripting language, such as VBScript, and many other programming languages as are well known may be used. (Java™ is a trademark of Sun Microsystems®, Inc.).

According to some embodiments, each system 916 is configured to provide web pages, forms, applications, data and media content to user (client) systems 912 to support the access by user systems 912 as tenants of system 916. As such, system 916 provides security mechanisms to keep each tenant's data separate unless the data is shared. If more than one MTS is used, they may be located in close proximity to one another (e.g., in a server farm located in a single building or campus), or they may be distributed at locations remote from one another (e.g., one or more servers located in city A and one or more servers located in city B). As used herein, each MTS could include logically and/or physically connected servers distributed locally or across one or more geographic locations. Additionally, the term “server” is meant to include a computing system, including processing hardware and process space(s), and an associated storage system and database application (e.g., OODBMS or RDBMS) as is well known in the art.

It should also be understood that “server system” and “server” are often used interchangeably herein. Similarly, the database object described herein can be implemented as single databases, a distributed database, a collection of distributed databases, a database with redundant online or offline backups or other redundancies, etc., and might include a distributed database or storage network and associated processing intelligence.

FIG. 10 also shows a block diagram of environment 910 further illustrating system 916 and various interconnections, in accordance with some embodiments. FIG. 10 shows that user system 912 may include processor system 912A, memory system 912B, input system 912C, and output system 912D. FIG. 10 shows network 914 and system 916. FIG. 10 also shows that system 916 may include tenant data storage 922, tenant data 923, system data storage 924, system data 925, User Interface (UI) 1030, Application Program Interface (API) 1032, PL/SOQL 1034, save routines 1036, application setup mechanism 1038, applications servers 10001-1000N, system process space 1002, tenant process spaces 1004, tenant management process space 1010, tenant storage area 1012, user storage 1014, and application metadata 1016. In other embodiments, environment 910 may not have the same elements as those listed above and/or may have other elements instead of, or in addition to, those listed above.

User system 912, network 914, system 916, tenant data storage 922, and system data storage 924 were discussed above in FIG. 9. Regarding user system 912, processor system 912A may be any combination of processors. Memory system 912B may be any combination of one or more memory devices, short term, and/or long term memory. Input system 912C may be any combination of input devices, such as keyboards, mice, trackballs, scanners, cameras, and/or interfaces to networks. Output system 912D may be any combination of output devices, such as monitors, printers, and/or interfaces to networks. As shown by FIG. 10, system 916 may include a network interface 920 (of FIG. 9) implemented as a set of HTTP application servers 1000, an application platform 918, tenant data storage 922, and system data storage 924. Also shown is system process space 1002, including individual tenant process spaces 1004 and a tenant management process space 1010. Each application server 1000 may be configured to tenant data storage 922 and the tenant data 923 therein, and system data storage 924 and the system data 925 therein to serve requests of user systems 912. The tenant data 923 might be divided into individual tenant storage areas 1012, which can be either a physical arrangement and/or a logical arrangement of data. Within each tenant storage area 1012, user storage 1014 and application metadata 1016 might be similarly allocated for each user. For example, a copy of a user's most recently used (MRU) items might be stored to user storage 1014. Similarly, a copy of MRU items for an entire organization that is a tenant might be stored to tenant storage area 1012. A UI 1030 provides a user interface and an API 1032 provides an application programmer interface to system 916 resident processes to users and/or developers at user systems 912. The tenant data and the system data may be stored in various databases, such as Oracle™ databases.

Application platform 918 includes an application setup mechanism 1038 that supports application developers' creation and management of applications, which may be saved as metadata into tenant data storage 922 by save routines 1036 for execution by subscribers as tenant process spaces 1004 managed by tenant management process 1010 for example. Invocations to such applications may be coded using PL/SOQL 34 that provides a programming language style interface extension to API 1032. A detailed description of some PL/SOQL language embodiments is discussed in commonly assigned U.S. Pat. No. 7,730,478, titled METHOD AND SYSTEM FOR ALLOWING ACCESS TO DEVELOPED APPLICATIONS VIA A MULTI-TENANT ON-DEMAND DATABASE SERVICE, by Craig Weissman, filed Sep. 21, 2007, which is hereby incorporated by reference in its entirety and for all purposes. Invocations to applications may be detected by system processes, which manage retrieving application metadata 1016 for the subscriber making the invocation and executing the metadata as an application in a virtual machine.

Each application server 1000 may be communicably coupled to database systems, e.g., having access to system data 925 and tenant data 923, via a different network connection. For example, one application server 10001 might be coupled via the network 914 (e.g., the Internet), another application server 1000N−1 might be coupled via a direct network link, and another application server 1000N might be coupled by yet a different network connection. Transfer Control Protocol and Internet Protocol (TCP/IP) are typical protocols for communicating between application servers 1000 and the database system. However, other transport protocols may be used to optimize the system depending on the network interconnect used.

In certain embodiments, each application server 1000 is configured to handle requests for any user associated with any organization that is a tenant. Because it is desirable to be able to add and remove application servers from the server pool at any time for any reason, there is preferably no server affinity for a user and/or organization to a specific application server 1000. In some embodiments, therefore, an interface system implementing a load balancing function (e.g., an F5 Big-IP load balancer) is communicably coupled between the application servers 1000 and the user systems 912 to distribute requests to the application servers 1000. In some embodiments, the load balancer uses a least connections algorithm to route user requests to the application servers 1000. Other examples of load balancing algorithms, such as round robin and observed response time, also can be used. For example, in certain embodiments, three consecutive requests from the same user could hit three different application servers 1000, and three requests from different users could hit the same application server 1000. In this manner, system 916 is multi-tenant, wherein system 916 handles storage of, and access to, different objects, data and applications across disparate users and organizations.

As an example of storage, one tenant might be a company that employs a sales force where each call center agent uses system 916 to manage their sales process. Thus, a user might maintain contact data, leads data, customer follow-up data, performance data, goals and progress data, etc., all applicable to that user's personal sales process (e.g., in tenant data storage 922). In an example of a MTS arrangement, since all of the data and the applications to access, view, modify, report, transmit, calculate, etc., can be maintained and accessed by a user system having nothing more than network access, the user can manage his or her sales efforts and cycles from any of many different user systems. For example, if a call center agent is visiting a customer and the customer has Internet access in their lobby, the call center agent can obtain critical updates as to that customer while waiting for the customer to arrive in the lobby.

While each user's data might be separate from other users' data regardless of the employers of each user, some data might be organization-wide data shared or accessible by a plurality of users or all of the users for a given organization that is a tenant. Thus, there might be some data structures managed by system 916 that are allocated at the tenant level while other data structures might be managed at the user level. Because an MTS might support multiple tenants including possible competitors, the MTS should have security protocols that keep data, applications, and application use separate. Also, because many tenants may opt for access to an MTS rather than maintain their own system, redundancy, up-time, and backup are additional functions that may be implemented in the MTS. In addition to user-specific data and tenant specific data, system 916 might also maintain system level data usable by multiple tenants or other data. Such system level data might include industry reports, news, postings, and the like that are sharable among tenants.

In certain embodiments, user systems 912 (which may be client machines/systems) communicate with application servers 1000 to request and update system-level and tenant-level data from system 916 that may require sending one or more queries to tenant data storage 922 and/or system data storage 924. System 916 (e.g., an application server 1000 in system 916) automatically generates one or more SQL statements (e.g., SQL queries) that are designed to access the desired information. System data storage 924 may generate query plans to access the requested data from the database.

Each database can generally be viewed as a collection of objects, such as a set of logical tables, containing data fitted into predefined categories. A “table” is one representation of a data object, and may be used herein to simplify the conceptual description of objects and custom objects according to some embodiments. It should be understood that “table” and “object” may be used interchangeably herein. Each table generally contains one or more data categories logically arranged as columns or fields in a viewable schema. Each row or record of a table contains an instance of data for each category defined by the fields. For example, a CRM database may include a table that describes a customer with fields for basic contact information such as name, address, phone number, fax number, etc. Another table might describe a purchase order, including fields for information such as customer, product, sale price, date, etc. In some multi-tenant database systems, standard entity tables might be provided for use by all tenants. For CRM database applications, such standard entities might include tables for account, contact, lead, and opportunity data, each containing pre-defined fields. It should be understood that the word “entity” may also be used interchangeably herein with “object” and “table”.

In some multi-tenant database systems, tenants may be allowed to create and store custom objects, or they may be allowed to customize standard entities or objects, for example by creating custom fields for standard objects, including custom index fields. U.S. Pat. No. 7,779,039, titled CUSTOM ENTITIES AND FIELDS IN A MULTI-TENANT DATABASE SYSTEM, by Weissman, et al., and which is hereby incorporated by reference in its entirety and for all purposes, teaches systems and methods for creating custom objects as well as customizing standard objects in a multi-tenant database system. In some embodiments, for example, all custom entity data rows are stored in a single multi-tenant physical table, which may contain multiple logical tables per organization. In some embodiments, multiple “tables” for a single customer may actually be stored in one large table and/or in the same table as the data of other customers.

These and other aspects of the disclosure may be implemented by various types of hardware, software, firmware, etc. For example, some features of the disclosure may be implemented, at least in part, by machine-readable media that include program instructions, state information, etc., for performing various operations described herein. Examples of program instructions include both machine code, such as produced by a compiler, and files containing higher-level code that may be executed by the computer using an interpreter. Examples of machine-readable media include, but are not limited to, magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD-ROM disks; magneto-optical media; and hardware devices that are specially configured to store and perform program instructions, such as read-only memory devices (“ROM”) and random access memory (“RAM”).

While one or more embodiments and techniques are described with reference to an implementation in which a service cloud console is implemented in a system having an application server providing a front end for an on-demand database service capable of supporting multiple tenants, the one or more embodiments and techniques are not limited to multi-tenant databases nor deployment on application servers. Embodiments may be practiced using other database architectures, i.e., ORACLE®, DB2® by IBM and the like without departing from the scope of the embodiments claimed.

Any of the above embodiments may be used alone or together with one another in any combination. Although various embodiments may have been motivated by various deficiencies with the prior art, which may be discussed or alluded to in one or more places in the specification, the embodiments do not necessarily address any of these deficiencies. In other words, different embodiments may address different deficiencies that may be discussed in the specification. Some embodiments may only partially address some deficiencies or just one deficiency that may be discussed in the specification, and some embodiments may not address any of these deficiencies.

While various embodiments have been described herein, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present application should not be limited by any of the embodiments described herein, but should be defined only in accordance with the following and later-submitted claims and their equivalents. 

1. A computer-implemented method comprising: generating, by a database system, a cluster of records from a group of records based on one or more keys; splitting, by the database system, the cluster of records into multiple subsets of records with each subset of records having fewer number of records than the cluster of records, wherein the splitting the cluster of records into multiple subsets of records is based on a number of records in the cluster of records exceeding a threshold; causing, by the database system, duplicate sets of records in each of the subsets of records to be identified, wherein a duplicate set of records includes one or more records, and wherein when a duplicate set of records includes two or more records, the two or more records are duplicates of one another; merging, by the database system, all of the duplicate sets of records identified from the multiple subsets of records forming a first group of duplicate sets of records; and forming, by the database system, a representative set of records based on selecting a representative record from each of the duplicate sets in the first group of duplicate sets of records.
 2. The method of claim 1, wherein when a duplicate set of records includes two or more records, any one of the two or more records is selectable as a representative record, and wherein when a duplicate set of records includes only one record, the one record is a representative record.
 3. The method of claim 2, wherein merging all of the duplicate sets of records identified from the multiple subsets of records comprises merging two duplicate sets of records when the two duplicate sets of records share a common record.
 4. The method of claim 3, wherein merging two duplicate sets of records comprises: selecting, by the database system, a record from a first duplicate set of records; comparing, by the database system, the selected record with each record in a second duplicate set of records; and merging, by the database system, the first duplicate set of records with the second duplicate set of records based on matching the selected record with any one record in the second duplicate set of records.
 5. The method of claim 4, wherein merging the first duplicate set of records with the second duplicate set of records comprises merging a duplicate set of records with few records to a duplicate set of records with more records.
 6. The method of claim 5, further comprising: splitting the representative set of records into multiple subsets of records with each subset of records having fewer number of records than the representative set of records when a number of records in the representative set of records exceeds the threshold; and repeating the steps of causing duplicate sets of records, merging all the duplicate sets of records, and forming a representative set with the multiple subsets of records.
 7. The method of claim 5, further comprising: causing duplicate sets of records in the representative set of records to be identified forming a second duplicate sets of records; and forming a third duplicate set of records by merging the first duplicate sets of records with the second duplicate sets of records.
 8. The method of claim 7, wherein a duplicate set of records is implemented using a linked list having a head node and a body node for each record in the duplicate set of records, wherein size information of the duplicate set of records and an identification information of the duplicate set of records are stored in the head node, and wherein merging the first duplicate set of records with the second duplicate set of records comprises merging a linked list associated with the first duplicate set of records with a linked list associated with the second duplicate set of records.
 9. An apparatus for identifying duplicate records in a database object, the apparatus comprising: one or more processors; and a non-transitory computer readable medium storing a plurality of instructions, which when executed, cause the one or more processors to: generate a cluster of records from a group of records based on one or more keys; split the cluster of records into multiple subsets of records with each subset of records having fewer number of records than the cluster of records, wherein the splitting the cluster of records into multiple subsets of records is based on a number of records in the cluster of records exceeding a threshold; cause duplicate sets of records in each of the subsets of records to be identified, wherein a duplicate set of records includes one or more records, and wherein when a duplicate set of records includes two or more records, the two or more records are duplicates of one another; merge all of the duplicate sets of records identified from the multiple subsets of records forming a first group of duplicate sets of records; and form a representative set of records based on selecting a representative record from each of the duplicate sets in the first group of duplicate sets of records.
 10. The apparatus of claim 9, wherein when a duplicate set of records includes two or more records, any one of the two or more records is selectable as a representative record, and wherein when a duplicate set of records includes only one record, the one record is a representative record.
 11. The apparatus of claim 10, wherein merging all of the duplicate sets of records identified from the multiple subsets of records comprises merging two duplicate sets of records when the two duplicate sets of records share a common record.
 12. The apparatus of claim 11, wherein merging two duplicate sets of records comprises: selecting a record from a first duplicate set of records; comparing the selected record with each record in a second duplicate set of records; and merging the first duplicate set of records with the second duplicate set of records based on matching the selected record with any one record in the second duplicate set of records.
 13. The apparatus of claim 12, wherein merging the first duplicate set of records with the second duplicate set of records comprises merging a duplicate set of records with few records to a duplicate set of records with more records.
 14. The apparatus of claim 13, further comprising: splitting the representative set of records into multiple subsets of records with each subset of records having fewer number of records than the representative set of records when a number of records in the representative set of records exceeds the threshold; and repeating the steps of causing duplicate sets of records, merging all the duplicate sets of records, and forming a representative set with the multiple subsets of records.
 15. The apparatus of claim 13, further comprising: causing duplicate sets of records in the representative set of records to be identified forming a second duplicate sets of records; and forming a third duplicate set of records by merging the first duplicate sets of records with the second duplicate sets of records.
 16. The apparatus of claim 15, wherein a duplicate set of records is implemented using a linked list having a head node and a body node for each record in the duplicate set of records, wherein size information of the duplicate set of records and an identification information of the duplicate set of records are stored in the head node, and wherein merging the first duplicate set of records with the second duplicate set of records comprises merging a linked list associated with the first duplicate set of records with a linked list associated with the second duplicate set of records.
 17. A computer program product comprising computer-readable program code to be executed by one or more processors when retrieved from a non-transitory computer-readable medium, the program code including instructions to: generate a cluster of records from a group of records based on one or more keys; split the cluster of records into multiple subsets of records with each subset of records having fewer number of records than the cluster of records, wherein the splitting the cluster of records into multiple subsets of records is based on a number of records in the cluster of records exceeding a threshold; cause duplicate sets of records in each of the subsets of records to be identified, wherein a duplicate set of records includes one or more records, and wherein when a duplicate set of records includes two or more records, the two or more records are duplicates of one another; merge all of the duplicate sets of records identified from the multiple subsets of records forming a first group of duplicate sets of records; and form a representative set of records based on selecting a representative record from each of the duplicate sets in the first group of duplicate sets of records.
 18. The computer program product of claim 17, wherein when a duplicate set of records includes two or more records, any one of the two or more records is selectable as a representative record, and wherein when a duplicate set of records includes only one record, the one record is a representative record.
 19. The computer program product of claim 18, wherein merging all of the duplicate sets of records identified from the multiple subsets of records comprises merging two duplicate sets of records when the two duplicate sets of records share a common record.
 20. The computer program product of claim 19, wherein merging two duplicate sets of records comprises: selecting a record from a first duplicate set of records; comparing the selected record with each record in a second duplicate set of records; and merging the first duplicate set of records with the second duplicate set of records based on matching the selected record with any one record in the second duplicate set of records.
 21. The computer program product of claim 20, wherein merging the first duplicate set of records with the second duplicate set of records comprises merging a duplicate set of records with few records to a duplicate set of records with more records.
 22. The computer program product of claim 21, further comprising: splitting the representative set of records into multiple subsets of records with each subset of records having fewer number of records than the representative set of records when a number of records in the representative set of records exceeding the threshold; and repeating the steps of causing duplicate sets of records, merging all the duplicate sets of records, and forming a representative set with the multiple subsets of records.
 23. The computer program product of claim 21, further comprising: causing duplicate sets of records in the representative set of records to be identified forming a second duplicate sets of records; and forming a third duplicate set of records by merging the first duplicate sets of records with the second duplicate sets of records.
 24. The computer program product of claim 23, wherein a duplicate set of records is implemented using a linked list having a head node and a body node for each record in the duplicate set of records, wherein size information of the duplicate set of records and an identification information of the duplicate set of records are stored in the head node, and wherein merging the first duplicate set of records with the second duplicate set of records comprises merging a linked list associated with the first duplicate set of records with a linked list associated with the second duplicate set of records. 